Provisional dental implant for preparing an alveolus

ABSTRACT

The present invention relates to a temporary dental implant intended to prepare the alveola of an extracted tooth so that a selected dental implant can be inserted later. It also involves the use of this temporary dental implant from a functional and/or aesthetic point of view. It has, in addition, as its object kits, methods and tools, notably resin models, that can be used for the application or preparation of the above implants.

[0001] The present invention relates to a temporary dental implantintended to prepare the alveola of an extracted tooth with the intentionof installing subsequently a selected dental implant. It also relates tothe use of this temporary dental implant from a medical, functionaland/or aesthetic viewpoint. It also relates to kits, methods and tools,especially resin models, used for the application, preparation ormorphological selection of the above implants.

[0002] The natural tooth is anchored in a cavity called the alveola, inthe maxillary bone. This tooth is extracted when it is affected bylesions that are too serious to be treated: deep caries, parodontalpouch, rift, fractures, abscesses, traumatic injury. The insertion of adental implant can in such cases be the best solution applicable for itsreplacement.

[0003] The implantation is the result of a prudent and considered stepthe aim of which is to create ties to the maxilla or the mandible whichwill be stable, resistant, effective, non iatrogenic and durable and onwhich is fitted a detachable or fixed prosthesis offering the patientwho is partially or completely toothless, adequate function,satisfactory comfort and an aesthetic appearance suitable for socialfunction.

[0004] As far as the implantation is concerned, two techniques arebasically used at the present time:

[0005] a) The prostheses on osteo-integrated implants which areartificial roots made of titanium and which are stabilized by boneankylosis. The masticatory force is transmitted to the bone without anyreduction in power, due to the absence of the alveolo-dental ligamentwhich is an important factor in protecting the teeth against impact,overload, and the risk of fracture.

[0006] b) The transplants or other dental grafts, which do not have thedisadvantages of the above approach but require the availability of asuitable adequate and generally non functional donor tooth.

[0007] Dental transplantations and reimplantations have been carried outfor several decades and a variety of techniques have been described.

[0008] Another possible technique, described recently in the patentapplication WO 00/21456, proposes the replacement of lost teeth bypermanent false teeth connected to the maxillaries by the same tissueelements as natural teeth, i.e. a cement, an alveolo-dental ligament andan alveolar bone and allowing normal attachment of the gum to the neckof the implant. This technique allows the periodontium to exertadvantageously its normal physiological role, which is basically todampen the impact of mastication.

[0009] For a long time, oral implants have been synonymous withcomplications.

[0010] The technique of oral implantation actually comprises the risksof failures and contra-indications mainly associated with deficienciesin the bone involving its volume and density, poor vascular supply tocertain bone regions, possible overheating of tissues during thedrilling of the alveolas which can result in peri-implant tissuenecrosis, and infections basically associated with buccal flora orradicular debris or dental filler sometimes left in the bone afterextraction.

[0011] Previous careful examination, previous buccal cleaning, dentaland parodontal, antibiotic cover during the procedure, a surgicalprotocol that complies with the rules and findings based on scientificexperience allows the risk of failure to be kept below 5%.

[0012] Thus, the present invention proposes, for the first time, asolution allowing the risk of failure to be reduced while allowingbiological stimulation of the tissues. It involves a temporary alveolardental preparation implant intended to receive the final implant. Itoperates both for osteo-integrable implants as well as implants withcement and alveolo-implant ligament (Patent WO 00/21456). Thepreparation implant consists of a coronary part and a radicular part,the latter being hollow and partially porous. The compartment created inthe interior of the preparation implant is intended to contain an activecomposition that is released directly at the alveolar site presenting arisk of infection, via the pores or channels responsible for theporosity of the radicular part of the preparation implant.

[0013] Another advantage of the present invention is the conservation orremodeling of the size of the alveola adapted for the insertion of theimplant selected at the start.

[0014] The alveolar preparation implant also allows control of thehealing of the alveola in such a way as to optimize osteo-integration orparodonto-integration.

[0015] So, one initial aim of the present application involves atemporary alveolar dental preparation implant, characterized in that itforms a separable coronary part and a radicular part and in that theradicular part is hollow and partially porous. The dental implantaccording to the invention is a temporary implant, i.e. intended toprepare an alveola with the intention of inserting a definitive implanton a subsequent occasion. So, it is intended to be placed in a subjectin a temporary manner, during the period of time needed for thepreparation of the definitive implant, and allows preparation of thesite of implantation to increase the success of the treatment, and toshorten the overall time of the process. Typically, it involves atemporary non-osteo-integrable implant, i.e. non integrated in apermanent manner in the bone.

[0016] Another aim of the present application involves the use of adental implant comprising of a separable coronary part and a radicularpart, the radicular part being hollow and partially porous, for thepreparation of a composition or a kit intended for temporaryimplantation in a subject for the preparation of an alveola intended toreceive a definitive implant. The temporary implantation means that thetemporary implant is maintained in the alveola for a fixed period oftime, typically from one to five months, for example from one to twomonths, then it is removed. Typically, it is non-osteo-integrable, i.e.non integrated in a permanent manner in the bone.

[0017] Another aim of the present application involves a method ofdental implantation in a subject, comprising a preparation step for analveola intended to receive a definitive implant by inserting atemporary implant comprising a separable coronary part and a radicularpart, the radicular part being hollow and partially porous.

[0018] One particular method comprising (i) the extraction of anaffected tooth, (ii) the insertion in the alveola of said tooth of atemporary implant comprising a separable coronary part and a radicularpart, the radicular part being hollow and partially porous and (iii),the removal of the temporary implant and the insertion of a definitiveimplant in the alveola prepared in such a manner. Step (i) is optionalin so far as the implantation can be carried out at a site from whichthe tooth has already been removed.

[0019] Another aim of the invention is also the preparation of a productor kit intended to promote maxillary or mandibular bone reconstructionin patients for whom the insertion of an implant would require a bonegraft beforehand, an additional and complex surgical step, requiring anadditional period of at least four months. So, the alveolar preparationimplant allows control of the healing in an optimal manner, and, in thecase of parodonto-integrable implants which require preparation in thelaboratory using tissue engineering techniques, to maintain theappropriate morphology of the alveola during the period needed for thein vitro steps.

[0020] Other aspects of the present application involve particularlydisposable models of teeth which can be used as a gauge, as well as inkits, comprising for example several sets of temporary implants ordisposable models.

LEGENDS TO THE FIGURES

[0021] FIG. no. 1: Scheme of a section of a natural tooth: enamel (e),dentine (d), maxillary bone (o), gum (g), ligament (l).

[0022] FIG. no. 2: Scheme of a section of a tooth affected by lesionsthat are too serious for treatment: deep caries, parodontal pouch,splitting, fracture, abscess, traumatic injury.

[0023] FIG. no. 3: Example of a disposable, resin model, including ameans of gripping (m) located on the corresponding part to the coronaryregion of a tooth and allowing one to gauge after extraction of theaffected tooth, the size of the preparation implant and hence thedefinitive implant required for the replacement of the tooth. This modelcan be monochrome but should allow the neck of the tooth to be seen toinsert it in the gum.

[0024] FIG. no. 4: Temporary alveolar dental preparation implant. Itallows the size of the alveola to be maintained suitable for theinsertion of the definitive implant determined at the start, andcontrols the healing process. It is hollow, to allow, via pores, slowrelease of active material which will prepare the site for receiving thedefinitive implant. It is covered and sealed by a crown of resin orgrooved composite, for example, which can be sutured to the gum or stuckto the neighboring teeth. This configuration allows the immediatereplacement of the extracted tooth for cosmetic reasons.

[0025] Structure and Materials Involved in the Alveolar DentalPreparation Implant:

[0026] The present invention involves an alveolar dental preparationimplant intended to receive the definitive implant. The preparationimplant consists of a separable coronary part and a radicular part.

[0027] The coronary part covers and seals the radicular part. The sealcan be ensured by any type of material allowing a temporary attachmentof the two parts of the implant. According to one preferred embodimentof the invention, the two parts are linked by a temporary cement.According to another preferred embodiment of the invention, the coronarypart is fitted, on its palatine face, with a channel which the operatorcan use to support an instrument, since, by carrying out a levermovement, he can separate more easily, the coronary part from theradicular part, if required.

[0028] The coronary part of the preparation implant is adapted to theradicular part of this implant, selected on the basis of the extractedtooth to be replaced, and can be made of any biocompatible materialmechanically suitable. It can involve for example a simplemethyl-methacrylate resin. According to one preferred embodiment of theinvention, the coronary part is made of a composite material. Accordingto another preferred embodiment of the invention, the crown is made of acomposite material based on loaded methylmethacrylate resin.

[0029] This crown can be attached to the neighboring teeth to stabilizethe temporary implant. As an alternative, this crown can be held bysutures to the gum and so keep the radicular part in the alveola. Inthis case, the crown comprises channels and/or grooves that act tostabilize the sutures (cf: Drawing no.1). This crown is adjusted toremain in sub-occlusion during all movements of the mandible, such thatthe sub-adjacent tissues can undergo healing without being subject tosignificant compression. It also has the aesthetic advantage of allowingimmediate replacement of an extracted tooth following the selection ofthe suitable morphological model. The sutures used can be any type ofbio-degradable or non biodegradable material with a functional life ofat least four to five weeks. According to one preferred embodiment ofthe invention, the sutures used are made of non biodegradable teflon.

[0030] The radicular part of the temporary implant can have a variety ofshapes and dimensions, basically determined by the type of tooth and bythe type of implant.

[0031] In the case where a defined parodonto-integrable implant isplanned, the radicular part of the preparation implant has an overallshape matching that of the extracted tooth that is to be replaced.However, it is also possible to alter the alveola, for example with bonedrills, after the tooth extraction, to fit as closely as possible one ofthe shape models available. The model and the preparation implant willbe slightly greater than the definitive implant with cement andligament, to leave a space of 50 to 300 micrometers, for example,intended for the development of the ligament and the alveolar boneattaching the ligament to the rest of the maxilla. This space avoids theformation of permanent compression zones between the implant root andthe maxillary bone during the insertion of the definitiveparodonto-integrable implant.

[0032] In the case where the planned definitive implant isosteo-integrable, the shape of the alveolar preparation implant isgenerally cylindrical or slightly conical or with steps according to thetype of implant envisaged. Its length is that of the definitive implantenvisaged. On the other hand, its diameter is generally smaller, forexample about 1 millimeter, to allow insertion in the healed bone ofwhorls of the definitive osteo-integrable implant and its good initialstability which is essential for a satisfactory outcome.

[0033] The radicular part of the alveolar preparation implant, accordingto the invention, can be of any biocompatible material which issufficiently mechanically resistant to avoid the risk of fracture.According to a preferred method of the invention, the preparation rootis made of biocompatible plastic, for example polycarbonate,polytetrafluoroethylene or methyl polymethacrylate.

[0034] The radicular part of the alveolar preparation implant, accordingto the invention, includes a cavity able to contain active composition.Furthermore, the radicular part includes holes or channels with adiameter sufficient to ensure effective diffusion of the activecomposition, in the alveola, for example over a period of 4 to 5 weeks,preferably 6 to 8 weeks.

[0035] The cavity in the radicular part of the alveolar preparationimplant can, according to another embodiment of the invention, bedivided into compartments and hence contain, in each compartment, aparticular active composition which will act preferentially at a givenalveolar region.

[0036] The number, position and diameter of the pores can be adjusted bya man skilled in the art, as a function of the type of tooth, the activecomposition, etc. In addition, it is also possible, according to thelength of treatment, to refill the cavity of the radicular part, bywithdrawing it from the coronary part, after implantation.

[0037] Active Material Released by the Radicular Part of the AlveolarPreparation Implant:

[0038] The active composition that the cavity, described in the lastparagraph, can contain, can be, for example, in the form of a solid orliquid, in the form of a gel or paste or even in a micro-encapsulatedform. It can contain any biologically active compound the release ofwhich into the alveola is desired.

[0039] The active composition can contain:

[0040] One or more antibiotics, to decontaminate the implant site; itcan be for example tetracycline. It can also be metronidazole.

[0041] an unsaponifiable material, for example maize, soya or avocado,which promotes collagenic healing, and/or

[0042] a vitamin (with the same aim), and/or

[0043] one or more growth factors, to accelerate healing, (for examplePDGF, TGFb, IGF, EGF, BMP, amelogenins, etc.) and/or

[0044] one or more hemostatic agents, and/or

[0045] one or more hormones, like for example dexamethasone, promotingtissue mineralization, and/or

[0046] one or more other compounds to prepare the site of the implant,if necessary obtained by genetic engineering.

[0047] Kits

[0048] The present invention also offers, in an advantageous manner, anassembly or kit comprising several radicular parts as defined above, ofdifferent sizes and/or shapes. More preferably, it involves a kitcomprising radicular parts suited to the main tooth shapes encounteredin human beings, more particularly to the 26 tooth shapes. According tothe extracted tooth, the professional therefore has at his disposal arange of preparation implants, allowing him to select the most suitable.

[0049] As indicated, the invention also provides tooth models (see FIG.no. 3), which can be used for example as a gauge. Typically, thesemodels are disposable, and made of a biocompatible material, preferablyin resin or a resin base. The model can have, on its vestibular face, agripping spike which allows it to be manipulated by the professionalusing pincers or needle-holder tweezers, and a hole through which asafety wire can be threaded. The model can be monochrome, but it allowsadvantageously a view of the neck of the tooth to insert it in the gum.Several models (up to 26), suited to the different types of morphologyof the roots of a human being, allow the vast majority of requirementsto be met. The professional will be able, with the help of the modelsavailable, to select the shape best suited to the alveolar preparationimplant.

[0050] Thus, the present invention offers the professional a preparationkit for the insertion of a dental implant, which comprises:

[0051] 1 or more models (preferably 26 models) allowing one to gauge thesize and/or shape of the appropriate preparation implant and so that ofthe definitive implant, and/or

[0052] 1 or more models (preferably 26 models) of alveolar preparationimplants, of corresponding morphology or of radicular parts of suchpreparation implants, and/or

[0053] 1 or more models (preferably 42 models) of grooved crowns, forthe sutures and for sub-occlusion, and/or

[0054] 1 or more models (preferably 42 models) of temporary crowns tocontrol in sub-occlusion or occlusion (these crown can also serve as thedefinitive implant), and/or

[0055] one or more active compositions, intended for insertion into thehollow radicular part of the alveolar preparation implant.

[0056] It is understood that these different items can be packaged in avariety of ways, for example in sachets, boxes, etc., preferably assingle items, generally under sterile conditions.

[0057] Use/Insertion

[0058] The insertion of the alveolar preparation implant, according tothe invention, comprises insertion of the radicular part and thecoronary part which covers and seals the former.

[0059] The installation of the assembly can be helped by the previoususe of one or more tooth models made in biocompatible material, asdescribed above. The model allows one to gauge, after extraction of thetooth to be replaced, the size of the alveola, to modify it if required,and to select the preparation implant of the corresponding shape, aswell as the future definitive implant.

[0060] After insertion, the temporary dental implant is held in place byany suitable technique (adhesive, suture, etc.). Preferably, it is heldby suturing using thread in biodegradable material or by adhesion of thecoronary part to the neighboring teeth, using a composite material.

[0061] When the definitive implant is ready and/or when the alveolaintended to receive it has healed sufficiently, the temporary implant isremoved and replaced by the definitive implant. This period isdetermined by the professional in terms of the individual case involved,and can range from several weeks to several months, generally 1 to 6months, advantageously 1 to 3 months.

[0062] The subsequent repair of a tissue lesion (extraction, fracture,drilling of the alveola for example) goes through three successivephases, more or less overlapping an inflammatory phase, a cellproliferation phase and a tissue remodeling phase.

[0063] The inflammatory phase triggers the process by contributingimmunity—related components, the phagocytosis of the injured anddestroyed materials and bacteria present, by activation of macrophages.This is an overall destructive phase.

[0064] The expansion of cytokines and growth factors, especially PDGFreleased by blood platelets during coagulation, initiates the followingphases directed at tissue repair.

[0065] The growth factors that have a significant action on cellproliferation are PDGF, TGFb and IGF. After a tooth extraction, thecells that proliferate are the residual fibroblasts, peri-vascularundifferentiated cells and medullary bone cells. The proliferation phasestarts after 48 hours and continues for 2 to 3 weeks after any trauma.It results in what is called granulation tissue which reaches a maximumaround 8 days.

[0066] PDGF and IGF also have an effect on the chemotaxis—themigration—of these cells towards the lesion to recolonize it.

[0067] The differentiation of cells before they are able to reconstitutethe tissue matrix is under the influence of many physico-chemicalfactors. Growth factors like EGF, IGF, TGF and BMP can have an effect,just like other more specific compounds like the amelogenins forexample. Mechanical constraints also play an important role at thislevel.

[0068] The remodelling phase is the period where the cells that haveceased to proliferate produce the specific matrix or matrices for thetissues to be repaired. For example, in the periodontium, a populationof fibroblasts will produce collagen which will re-establish theconjunctive fibers forming the tissue and giving it its resistance totension and the osteoblasts will secrete the mineralizable matrix whichwill undertake the production of crystals of hydroxy-apatite to providebone tissue. Cementoblasts coming into contact with the tooth roots, inthe parodontal lesions, re-establish the connection between theconjunctive fibers and the radicular surface by the regeneration of a<<cement>>.

[0069] As far as the established methods ofr osteo-integratedimplantation techniques are concerned, the permitted interval in healingbetween the extraction of the tooth affected and the insertion of theimplant intended to replace it is 6 to 12 months, increased by theperiod of osteo-integration which, itself, is 3 to 6 months (Adell etcoll., 1981).

[0070] The alveolar preparation implant and the methods according to theinvention, allow, by the release of suitable growth factors and acertain degree of physiological stimulation (reduced in comparison withthe normal constraints usually undergone by a tooth), acceleratedhealing and better preparation of the site of insertion of thedefinitive implant, be it osteo or parodonto-integrated. If it is foundthat too much or not enough activation reduces the bone repair, themechanical stimulation produced by the techniques of the inventioninvolving the alveola are appropriate by the fact that the crown placedon the preparation implant is in sub-occlusion and only transmits partof the pressure induced by mastication.

[0071] Thus, the technique according to the invention allows a reductionin the normal healing time by a factor of about three, and improves theconditions of integration or insertion of the definitive implant.

1. Temporary alveolar dental preparation implant characterized in thatit consists of separable coronary and radicular parts and in that theradicular part is hollow and partially porous.
 2. Temporary alveolardental preparation implant according to claim 1, characterized in thatthe coronary part covers and seals the radicular part preferably withthe help of a temporary cement.
 3. Temporary alveolar dental preparationimplant according to claim 2, characterized in that the coronary partcomprises of a channel allowing the dissociation, by carrying out alever action, of said coronary part and the radicular part.
 4. Temporaryalveolar dental preparation implant according to any of claims 2 or 3,characterized in that the coronary part is made of biocompatiblematerial, for example resin or composite.
 5. Temporary alveolar dentalpreparation implant according to claim 4, characterized in that thecoronary part is in simple methylmethacrylate resin or composite basedon loaded methylmethacrylate resin.
 6. Temporary alveolar dentalpreparation implant according to any of the preceding claims,characterized in that the radicular part has a shape suited to that ofthe extracted tooth, and preferentially, slightly larger than theparodonto-integrable receiving implant.
 7. Temporary alveolar dentalpreparation implant according to any of the claims 1 to 5, characterizedin that the radicular part has a cylindrical or slightly conical shapeor with steps, suitable for receiving a particular osteo-integrableimplant and, preferentially, slightly smaller than the receivingimplant.
 8. Temporary alveolar dental preparation implant according toany of the preceding claims, characterized in that the radicular part ismade of biocompatible material, preferably biocompatible plastic, forexample in polycarbonate, polytetrafluoroethylene or methylpolymethacrylate.
 9. Temporary alveolar dental preparation implantaccording to any of the preceding claims, characterized in that theradicular part includes a cavity that is able to contain one or moreactive compositions.
 10. Temporary alveolar dental preparation implantaccording to claim 9, characterized in that the cavity is divided intocompartments and so can contain, in each compartment, a particularactive composition which acts at a given part of the alveola. 11.Temporary alveolar dental preparation implant according to claim 9 or10, characterized in that the active composition is in solid or liquidform, a gel or paste or is micro-encapsulated.
 12. Temporary alveolardental preparation implant according to any of claims 9 to 11,characterized in that the active composition contains at least anantibiotic, for example tetracycline or metronidazole and/orunsaponifiable maize, soya or avocado and/or a vitamin and/or one ormore growth factors and/or one or more hemostatic agents and/or one ormore hormones, for example dexamethasone and/or one or more othercompounds preparing the receptor site of the implant, if requiredobtained by genetic engineering.
 13. Temporary alveolar dentalpreparation implant according to any of claims 9 to 12, characterized inthat the radicular part includes pores or channels with a diameter largeenough to ensure effective diffusion of the active material in thealveola.
 14. Radicular part of a temporary alveolar dental preparationimplant according to any of the preceding claims, characterized in thatthe radicular part is hollow and partially porous.
 15. Use of atemporary alveolar dental preparation implant according to one of claims1 to 9, for the preparation of a product intended to preserve theaesthetic appearance of a subject after the extraction of a tooth. 16.Use of a temporary alveolar dental preparation implant according to oneof claims 1 to 13, for the preparation of a product or kit intended topromote maxillary or mandibular bone reconstruction in a human being.17. Disposable model including a means of gripping located in the partcorresponding to the coronary region of a tooth, made of a biocompatiblematerial allowing one to assess the size of the alveolar preparationimplant according to any of the preceding claims, suitable for thereplacement of the extracted tooth.
 18. Model according to claim 17,characterized in that it is made of resin.
 19. Model according to one ofclaims 17 or 18, characterized in that it is monochrome but allows theneck of the tooth to be seen.
 20. Preparation kit for the insertion of atemporary alveolar dental preparation implant, according to any ofclaims 1 to 13, which comprises: 1 or more models (preferably 26 models)allowing one to assess the size and/or the shape of the suitablepreparation implant and so that of the definitive implant, and/or 1 ormore models (preferably 26 models) of alveolar preparation implants, ofcorresponding morphology or of the radicular parts of such preparationimplants, and/or 1 or more models (preferably 42 models) of groovedcrowns, for the sutures and in sub-occlusion, and/or 1 or more models(preferably 42 models) of temporary crowns to control in sub-occlusionor occlusion, and/or one or more active compositions, intended to beplaced in the hollow radicular part of the alveolar preparation implant.21. Use of a dental implant comprising a separable coronary andradicular parts, the radicular part being hollow and partially porous,for the preparation of a composition or a kit intended for a temporaryimplantation in a subject for the preparation of an alveola intended toreceive a definitive implant.
 22. Method of dental implantation in asubject, comprising (i) the extraction of an affected tooth, (ii) theinsertion in the alveola of said tooth of a temporary implant comprisinga separable coronary and radicular parts, the radicular part beinghollow and partially porous and capable of allowing the diffusion of oneor more active substances and (iii), the removal of the temporaryimplant and the insertion of a definitive implant in the alveola thathas been so prepared.